The flu and COVID-19 are distinct respiratory illnesses caused by different viruses: influenza viruses for the flu and SARS-CoV-2 for COVID-19. Both can lead to a range of symptoms affecting the nose, throat, and sometimes the lungs. A common concern is the possibility of experiencing both illnesses simultaneously.
Understanding Coinfection
It is possible to contract both influenza and COVID-19 simultaneously, a situation known as coinfection. Both are highly contagious respiratory viruses that spread through droplets expelled when an infected person coughs, sneezes, or talks.
While coinfection is possible, its prevalence can vary. Some studies indicate a global prevalence of COVID-flu coinfection around 14%. Coinfections involving two or more viruses are not uncommon, with some studies showing about 43% of hospitalized patients with flu-like symptoms testing positive for multiple viral infections.
Recognizing Symptoms and Risks
Both COVID-19 and the flu can present with similar symptoms, making distinction challenging. Common overlapping symptoms include fever, cough, fatigue, sore throat, runny or stuffy nose, muscle pain, body aches, and headache. Vomiting and diarrhea may also occur, more commonly in children with the flu.
A notable difference is that loss of taste or smell is more frequently associated with COVID-19. Coinfection carries increased health risks, leading to a higher likelihood of severe illness and complications such as pneumonia, respiratory failure, or myocarditis. Individuals at higher risk for severe outcomes include older adults, those who are immunocompromised, and people with underlying health conditions like asthma, diabetes, or heart disease.
Diagnosis and Management
Given the similar symptoms of flu and COVID-19, accurate testing is important for diagnosis. Healthcare providers can use multiplex PCR tests to detect and differentiate between multiple respiratory viruses, including SARS-CoV-2, influenza A, and influenza B, from a single patient sample. These tests help determine if a patient has one, both, or neither virus, especially during overlapping respiratory virus seasons.
Management of coinfection typically involves supportive care to alleviate symptoms. Antiviral medications may also be prescribed, depending on the patient’s condition and risk factors. For the flu, FDA-approved antiviral drugs like oseltamivir (Tamiflu) can be used, while for COVID-19, medications such as Paxlovid or molnupiravir may be prescribed. These antiviral treatments work best when started early to reduce symptom severity and duration.
Prevention Strategies
Several strategies can help reduce the risk of contracting either the flu or COVID-19, thereby preventing coinfection. Vaccination is a primary measure, with both annual flu shots and COVID-19 vaccines recommended. These vaccines help protect against severe illness, hospitalization, and death. It is safe to receive both vaccines at the same visit.
Practicing good hygiene habits is also a core prevention strategy. This includes frequent handwashing, using hand sanitizer, covering coughs and sneezes, and regularly cleaning frequently touched surfaces. Wearing masks in crowded or poorly ventilated settings can further reduce respiratory droplet transmission. Staying home when sick also helps prevent the spread of both viruses.